Poly-alpha-olefin compositions containing dialkyl-3, 3&#39;-thiodipropionates and a nitrogen containing compound



' synergistic combinations of stabilizers for United States Patent s 012604 POLY a OLEFIN colvrrbsmoNs CONTAINING DIALKYL 3,3 THIODIPROPIONATESANI) A NITROGEN CONTAINING COMPOUND Clarence E. Tholstrup, Kingsport,Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey No Drawing. Filed Mar. 23, 1960, Ser. No. 16,969 14Claims. (Cl. 260-4535) peratures usually result in oxidative degrationof the polymer. In addition, many uses of poly-a-olefins, such as inelectrical insulation and the like, often times expose the poly-m-olefinto elevated temperatures. To minimize oxidative deterioration inpoly-a-olefins, antioxidants or stabilizers are often times incorporatedtherein.

It is an object of this invention to provide new polya-olefincompositions having improved resistance to thermal degradation.

It is another object of this invention to provide new poly-a-olcfincompositions.

It is also an object of this invention to provide novel polyethylene andpolypropylene compositions containing synergistic combinations ofcompounds that improve the stability of the polyethylene andpolypropylene compositions against deterioration resulting from exposureto elevated temperatures.

Other objects of the invention will be apparent from the description andclaims that follow.

The present invention comprisespoly-a-olefin composition havingincorporated therein a stabilizer combination of a diester of3,3'-thiodipropionic acid and a hydroxyl'containing amine.

The diesters of 3,3'-thiodipropionic acid comprising the presentstabilizer combinations have the following formula II S(CH:CH:COR);

. wherein R is an alkyl radical generally having 4 to 20 icehydroxyl-containing amines or nitrogen-containing compounds having theformulas:

wherein R R R R R R R R R and R are and alkyl radicals having 1 to 18carbon atoms, and preferably l to 12 carbon atoms; and wherein R is analkyl radical or an alkoxy radical, both having 1 to 18 carbon atoms,and preferably 1 to 12 carbon atoms.

Typical hydroxyl-containing amines that can be suitably employed incombination with dialkyl-3,3-thiodipropionates include:

4-hydroxy-4'-methoxydiphenylamine, 4-hydroxy-4'-isobutoxydiphenylamine,4-hydroxy-4'-n-octyldiphenylamine,3-tert.-butyl-4'-hydroxydiphenylamine, 4-hydroxy-4-lauryldiphenylamine,2-tert.-butyl-4'-hydroxydiphenylamine,4-hydroxy-4'-stearyldiphenylamine, 3-stearyl-4-hydroxydiphenylamine,2,6-di-tert.-butyl-p-dimethylaminomethylphenol,2,G-dimethyl-p-distearylaminomethylphenol,2,6-di-tert.-octyl-p-dilaurylaminomethylphenol,2,6-distearyl-p-dimethylaminomethylphenol,2,6-dilauryl-p-diethylaminomethylphenol,N,N-bis(2-hydroxy-3-tert.-butyl-S-methylbenzyl) methylamine,N,N-bis(2-hydroxy-3-tert.-butyl-5-laurylbenzyl) laurylamine,N,N-bis(2-hydroxy-3-lauryl-5-stearylbenzyl)-nbutylamine,N,N-bis(2-hydroxy-3-stearyl-5-methylbenzyl) methylamine,N,N-bis(2-hydroxy-3-methyl-5-tert.-butylbenzyl) stearylamine,N-acetyl-p-aminophenol, N-n-butyryl-p-aminophenol,N-caprylyl-p-aminophenol, N-pelargonyl-p-aminophenol,N-myristoyl-p-aminophenol, N-lauroyl-p-aminophenol,N-palmitoyl-p-aminophenol, N-n-nonadecanoyl-p-aminophenol, and relatedhydroxyl-containing amines.

be used to stabilize a wide variety of solid poly-a-olefin cordance withthe invention. The subject stabilizer combinations are preferably usedin polyethylene and polypropylene, particularly polypropylene, althoughsuch polyu-olefins as poly(3-methylbutene-l), poly(4-methylpentene-lpoly(pentene-l poly( 3,3-dimethylbutene-1 poly(4,4-dimethylbutene-1),poly(octene-l), poly(decene-l) and the like can also be stabilized withthe subject stabilizer combinations. Both the so-called low density" andhigh density or high crystallinity polya-olefin compositions can bestabilized in accordance with the invention. Reference is made toFawcett et al. US. Patent No. 2,153,553 granted April 11, 1939, and tocopending applications Coover U.S. Serial No. 559,536, filed January 17,1956, now abandoned, and Coover et al. US. Serial No. 724,904, filedMarch 31, 1958, now abandoned, with regard to the preparation of variouspoly-a-olefin compositions that can be stabilized against thermaldegradation in accordance with the invention. The additive stabilizercombinations of the invention are especially useful for stabilizing thesolid resinous polye-oleiins having average molecular weights of atleast 15,000 and more usually at least 20,000, although the stabilizercombinations of the invention can also be utilized to stabilize theso-called poly-a-olefin waxes having lower average molecular weights ofusually 3,000 to 12,000.

The amount of the combination of the diester of 3,3- thiodipropionicacid and the hydroxyl-containing amine employed in poly-a-olefincompositions in accordance with the invention can be widely varied, thestabilizing amount of this combination usually varying with theparticular use to which the poly-a-olefin compositions are to be put.Concentrations of at least about .001% of each stabilizer component aresuitable, although about .001% to 5% for each stabilizer component aregenerally used, with about 0.1% to 3% of the diester of 3,3-thiodipropionic acid and about .0l% to 1% of the hydroxyl-containingamine being preferred, the concentration being based on the weight ofthe poly-a-olefin. We generally utilize the combination of the subjectstabilizers at a weight ratio of the diester of 3,3-thiodipropionic acidto the hydroxyl-containing amine in the range of H100 to 100/1, andpreferably l/50 to 50/1.

The stabilizer combinations of the invention can be incorporated orblended into poly-a-olefin compositions by the conventional methodsutilized for blending such materials into resins or plastics. Typical ofsuch methods that can be suitably employed include milling on heatedrolls, deposition from solvents, and dry blending. The stabilizers ofthe invention can be incorporated separately or together into thepoly-a-olefin compositions.

The stabilizer combinations of the present invention lend topoly-a-olefin compositions improved stability, and more particularly,improved stability against oxidative deterioration resulting fromexposure to elevated temperatures. In addition, poly-a-olefincompositions containing the stabilizer combinations of the inventionhave enhanced stability against deterioration resulting from exposure tosunlight or ultraviolet light. Thus, poly-aolefins stabilized inaccordance with the invention have an extended life expectancy and canbe used more effectively than unstabilized poly-a-oleiins for a widediversity of uses. Poly-a-olefins stabilized as described can be cast,extruded, rolled, or molded into sheets, rods, tubes, pipes, filamentsand other shaped articles, including the widely used films of thepolymers about .5 to 100 mils in thickness. The present compositions canbe used for coating paper, wire, metal foil, glass fiber fabrics,synthetic and natural textiles or fabrics, and other such materials.

The subject stabilizer combinations of dialkyl esters of3,3'-thiodipropionic acid and hydroxyl-containing amine are synergisticcombinations, namely, the stabilizing effect of such combinations inpoly-a-olefins is substantially greater than the additive efiect of theindividual components of the combination.

The invention is illustrated by the following examples of preferredembodiments thereof. In the following examples the stability of thepoly-a-olefins was determined by an oven storage test. The poly-e-olefinunder investigation is compression molded into a smooth sheet or plate.The plate is then cut into pieces weighing about 0.25 g. each. The 0.25g. samples of the molded polymer are then placed in an air oven at 160C. Samples are removed at intervals and each sample analyzed forperoxides. The oven storage life is the time required for initialperoxide formation in a sample of the polymer. To determine peroxideformation in the oven exposed samples, each 0.25 g. sample in questionis dissolved or suspended in 20 ml. of carbon tetrachloride and allowedto digest for 25 minutes. To this is added 20 ml. of a mixtureconsisting of 60% glacial acetic acid and 40% chloroform, and then 1.0ml. of a saturated aqueous solution of potassium iodide. The resultingmixture is allowed to react for two minutes, ml. of water is added todilute the mixture, and then a starch indicator is added. The resultingmixture is then back-titrated with 0.002 N sodium thiosulfate. 'Iheperoxide concentration, P, in milliequivalents per kilogram of polymeris given by the expression, P=8S, where S is the number of millilitersof 0.002 N sodium thiosulfate used.

EXAMPLE 1 Several samples of powdered polypropylene were mixed withdilauryl-3,3'-thiodipropionate and typical hydroxylcontaining amines ofthe invention, compression molded into plates A inch in thickness, andthe resulting molded samples evaluated with respect to stability by the160 C. oven storage test described above. The polypropylene was aplastic grade solid polypropylene having an average molecular weightgreater than 15,000, a density of about .91 and an inherent viscosity ofabout 1.48 as determined in tetralin at C. The results of the stabilitytests are summarized by the data set out in Table A below. Samples ofthe individual components of the various stabilizer combinations in thepolypropylene, as well as the polypropylene with no additive, wereincluded in the stability test for purposes of comparison. In Table A,dilauryl-3,3'-thiodipropionate is indicated as DLTDP. The concentrationsin Table A are based on the weight of the polypropylene.

As can be observed from the data set out in Table A above, combinationsof certain hydroxyl-containing amines and dilauryl-3,3thiodipropionateare synergistic combinations with respect to the stabilization ofpolypropylene, the stabilizing effect of such combinations beingsubstantially more than the additive stabilizing effect of thecomponents thereof. Similar synergism is demonstrated if solid plasticgrade polyethylene having an average molecular weight greater than15,000, a melt index of about 7.59 and a density of about .91 issubstituted for the polypropylene, or if distearyl-3,3'-thiodipropionate or di-n-octyl-3,3'-thiodipropionate issubstituted for the dilauryl-3,3'-thiodipropionate.

EXAMPLE 2 Other stabilizer combinations of the invention were evaluatedby geemethodidescribcd in Example 1 in the stabilization ofsolidiplastic grade polypropylene having an average molecular weightgreater than 15,000, a density of about .91 and an inherent viscosity ofabout 1.25 as determined in tetralin at 145 C. The results of the testare summarized by the data set out in Table B below. in Table B,dilauryl-3,3'-thiodipropionate is indicated as DLTDP." Theconcentrations in Table B are based I on the weight of thepolypropylene. i Table B Additive: Ovenlife at 160' 0. hours None 2 0.3%DLTDP 3 0.05% 4-hydroxy-4'-methoxydiphenylamine 12 0.05%'4-hydroxy-4'-mcthoxydiphenylamine+ 0.3% DLTDP 600.l%-N-lauroyl-p-aminophenol 4 0.l%-N-lauroyl-p-aminophenol+0.3% DLTDP-15 As observed from the data in Table B, dilauryl-3,3'-thiif solidplastic grade polyethylene having an averagemolecular weight greaterthan 15,000, a density of about .91 and a melt index of about 7.59 issubstituted for the polypropylene.

CHrN

R1 OH and wherein R is an alkyl radical having 4 to 20 carbon atoms, andabout .00l% to 5% by weight based on said poly-aolefin of anitrogen-containing compound selected from the group consisting ofcompounds having the formulas As used herein, inherent viscosity (i iscalculated from the formula wherein C is the concentration of thepolymer in grams per 100 cc. of tetralin and n, is the ratio of theviscosity of the solution of the polymer and tetralin to .that oftetralin. The viscosities are determined at 145 C.

The present invention thus provides novel poly-a-olefin compositionshaving improved stability against deterioration resulting from exposureto elevated temperatures, and particularly, it provides novelsynergistic stabilizer combinations for poly-a-olefin compositions;

Although the invention has been described in detail with reference topreferred embodiments thereof, it will be understood that variations andmodifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined by the appendedclaims. 1

I claim:

1. A solid poly-s-olefin composition comprising a solid poly-a-olefinprepared from an a-monoolefinic aliphatic hydrocarbon having 2 to 10carbon atoms containing a stabilizer combination comprising at leastabout .00l% by weight based on said poly-a-olefin of a diester of 3,3-

' thiodipropionic acid having the formula II 8(CHiCHrC O R)! IHO-Q-NHCR'no-Q-mro R! R OH OH R' and wherein R is an alkyl radical having 8 to 18carbon atoms, and about .00l% to 5% by weight based on said polyethyleneof nitrogen-containing compound selected from the group consisting ofcompounds having the formulas rro-Qmro RI H0 I cm v nr I 3' OH 1'10 l R1110 N CH: R"

Bil Q Q and wherein R is an alkyl radical having 8 to 18 carbon atoms,and about'.00l% to 5% by weight based on said polypropylene of anitrogen-containing compound selected from the group consisting ofcompounds having the formulas and R11 Q Q wherein R R R R R R, R", R, Rand R are are alkyl radicals having 1 to 18 carbon atoms, and wherein Ris selected from the group consisting of alkyl radicals'having 1 to 18carbon atoms and alkoxy radicals having 1 to 18 carbon radicals.

5. A solid poly-a-olefin composition comprising solid polypropylenecontaining a stabilizer combination comprising about .001% to 5% byweight based on said polypropylene of dilauryl-3,3-thiodipropionate andabout .001% to 5% by weight based on said polypropylene of anitrogen-containing compound selected from the group consisting ofcompounds having the formulas O HO-Q-NHPIR B Ra CHQN/ and 8 wherein R R,R R R, R, R R, R and R are alkyl radicals having 1 to 18 carbon atoms,and wherein R is selected from the group consisting of alkyl radicalshaving 1 to 18 carbon atoms and alkoxy radicals having 1 to 18 carbonradicals.

6. A solid poly-u-olefin composition comprising solid polypropylenecontaining a stabilizer combination comprising about .001% to 5% byweight based on said polypropylene of a diester of 3,3'-thiodipropionicacid having the formula swmcmclom: wherein R is an alkyl radical having8 to 18 carbon atoms and about .001% to 5% by weight based on saidpolypropylene of a nitrogen-containing compound having the formulanoQ-mrom wherein R is an alkyl radical having 1 to 12 carbon atoms.

7. A solid poly-a-olefin composition comprising solid polypropylenecontaining a stabilizer combination comprising about .00l% to 5% byweight based on said polypropylene of a diester of 3,3'-thiodipropionicacid having the formula wherein R is an alkyl radical having 8 to 18carbon atoms and about .001% to 5% by weight based on said polypropyleneof a nitrogen-containing compound having the formula wherein R R, R andR are alkyl radicals having 1 to 12 carbon atoms.

8. A solid poly-a-olefin composition comprising solid polypropylenecontaining a stabilizer combination comprising about .001% to 5% byweight based on said polypropylene of a diester of 3,3'-thiodipropionicacid having .the formula n 8(CH1CH1COR),

wherein R is an alkyl radical having 8 to 18 carbon atoms and about.001% to 5% by weight based on said polypropylene of anitrogen-containing compound having the formula OH OH R I ILCNCHQR"wherein R is an alkyl radical having 8 to 18 carbon atoms and about.001% to 5% by weight based on said polypropylene of anitrogen'containing compound having the formula Ru HOQNHQ wherein R isselected. from the group consisting ofalkyl radicals having 1 to 12carbon atoms and radicals having 1 to 12 carbon atoms.

10. A solid poly-a-olefin composition comprising solid polypropylenecontaining a stabilizer combination comprising .01% to 3% by weightbased on said polypropylene of dil-auryl-3,3'-thiodipropionate and .01%to 1% by weight based on v methoxydiphenylamine.

11. A solid poly-a-olefin composition comprising solid polypropylenecontaining a stabilizer combination comprising .01% to 3% by weightbased on said polypropylene of dilauryl-3,3-thiodipropionate and .01% to1% by weight based on said polypropylene of N -lauroyl-p-aminophenol.

12. A solid poly-a-olefin composition comprising solid polypropylenecontaining a stabilizer combination comprising .0I% to 3% by weightbased on said polypropylene of dilauryl-3,3'-thiodipropionate and .01%to 1% by weight based on said polypropylene of N,N-bis(2hydroxy-3-tert.-butyl-5-methylbenzyl)methylamine.

alkoxy saidpolypropylene of 4-hydroxy-4'- References Cited in the fileof this patent UNITED STATES PATENTS 2,448,799 Happoldt et a1. Sept. 7,1948 2,519,755 Gribbins Aug. 22, 1950 2,568,902 Thompson et a1. Sept.25, 1951 2,934,517

Young Apr. 26, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION (SEAL) Attest: I

ERNEST w. SWIDER I DAVID A Attesting Officer Commissioner of Patents

1. A SOLID POLY-A-OLEFIN COMPOSITION COMPRISING A SOLID POLY-A-OLEFINPREPARED FROM AN A-MONOOLEFINIC ALIPHATIC HYDROCARBON HAVING 2 TO 10CARBON ATOMS CONTAINING A STABILIZER COMINATION COMPRISING AT LEASTABOUT .001% BY WEIGHT BASED ON SAID POLY-A-OLEFIN OF A DIESTER OF3,3''THIODIPROPIONIC ACID HAVING THE FORMULA